Wind Turbine Day 16

_Day 16
The changes were a great success, I may even add a 5th
blade but I want to test it for a bit longer before making that call.
I also built a 5 Ohm dump load resistor today, nothing fancy
& only a few hours work, getting the wire length, diameter, type &
resistance was a lot more work.
The purpose of the dump load is when the turbine goes over
speed or your batteries are fully charge you will want to stop the turbine from
charging the batteries or creating to high a voltage. It would be easy to
create a device to electrically disconnect the turbine but without an
electrical load on the turbine it would accelerate in speed & can easily
get out of control. So the idea here is to automatically disconnect the turbine
in these conditions & automatically connect it to an electrical load that
can handle the high power which will slow it down.
The main thing is to make a decision on where you want this
extra power to go, it could power up a load of light bulbs although you would
have these lighting up at strange times during the day & night plus the
bulbs may blow. Actually adding or removing light bulbs until the turbine
behaves the way you want it would be a good idea but I had another solution
that I wanted to try.
One of the things I make & sell are hotwire cutters for
cutting polystyrene, these cutters use Nichrome Wire (Nickel plus chrome) which
is the same as any heating element wire. But because my hotwire cutters are 12
v I have a suitable range of different diameters that should work for a dump
load. I say suitable because a toaster wire or heater element would normally
have a larger diameter wire more suitable for mains power which would make it
more difficult to use, although not impossible by wiring it up in parallel but
a bit more precise & fiddly.
So when the wind was blowing I tested different
gauge(diameter) wires & especially the lengths until I found a combination
that would heat up enough during very strong winds to start to glow. This was a
lot of trial & error until I got it right & the wind always seems to
blow when it’s raining so I also got very wet.
The wire I ended up using is 5 ohms, 0.62mm & 1450mm
bare Nichrome wire which I already sell by the metre. I coiled the wire around
a strip of cement board & added a terminal post at each end as well as a
fixing post at each end for securing to the back of a wall mounted box that I have yet to buy. You can
use any none conductive strip that will not be affected by the heat but I had
some of this cement board available & it is cheap. I bought the terminal
posts for a few NZ dollars each but you could easily make something from some
old bolts if necessary. I don’t think the dump load needs any further
explanation, it’s fairly simple but depending on where you mount it you may
want to think about how safe this is, the wire can get very hot. Mine will
eventually be mounted inside a locked cabinet outside but I may still cover it
just in case.